My smaller dome goes faster. There was a lot of climbing up to, and down from, the hearth today. An injury would be easy to incur.

I didn't use the jack and plate. I could see from the 8th course that I would not notice mortar gaps if the dome base was covered. I held a couple of bricks with sticks and wedges and then cleaned up a bit after the ring was complete.

I actually reverted back to the IT and sticks, like you I could not see what was happening underneath the plywood disk, although easier and faster, I decided to go slower and able to get a visual alignment. I modified my IT to hold a smaller brick this week and going to give it a go this weekend. Good luck with you vent arch.

I built my inner vent arch *around* the "snout" of the dome. I back-cut the rear edges of the arch bricks to miss the dome, and chamfered the vent side to smooth the flow of smoke. There's a gap of ~0.1" all around the snout, and I packed the volume between the dome and the back-cuts with ceramic fiber.

I am posting this update with a question about heat management. I am trying to figure out if I need to weld up and install a throat adaptor to make the inner arch opening smaller.

I have been firing my oven for over three weeks. The most recent two got the floor to about 725 deg. F., but it is difficult to maintain floor temps over 625 without adding wood every ten minutes or so.

The oven is up to temp in about 90 minutes, but it uses much more wood than I thought it would need.

-No dome cracks (yet?), but a mortar crack appears in the vent arch on firing.

-The oven draws very well, even with a 6 " duratech (no smoke out the front).

I will build a decorative arch and a stone face on the front of the gabled house when I know that all is okay.

2" of FB Board under the floor (The hearth center is at about 120deg after 5+ hours)
3" of FB blanket over the dome and arch. I will fill the gable with vermiculite later.

I know that the inner arch heights and width are slightly too large, but the arch is a catenary, not semi-circular, so the opening area is a bit smaller than most arches with the same heights and widths.

In short, I am guessing that I am losing lots of heat up the chimney. Does it seem like a smaller inner arch opening would imporve the oven function?

You have made some major headway with the build since your last post. Interesting temperature observations. I am in the early stages of curing so it will be interesting to see how my build behaves. Anyway at those temps you should be able to do some cooking. Nice enclosure so far.

Since I started using a blast door (a misnomer; it doesn't have to "blast") I'm using less fuel and warming up faster. My door is a piece of 304 stainless with handles, which is shaped to fit against my vent arch when it's tipped back. It allows me to regulate the intake air (at the bottom) and the exhaust draft (how far it's tipped). I can still feel the door radiating heat, so I'll either insulate it or add a radiant shield inside. And a window... The extra heat that it retains promotes more complete combustion, too - the whole oven is a "rocket stove", so there's no need for plasma god fires.

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